National governments assign (or license) frequency bands to users for particular purposes, such as television broadcasting. In some instances, the frequency bands have “white space” between the bands to prevent interference. In other instances, some of the frequency bands may be unoccupied in a given geographic region. For example, a frequency band may be licensed for use in Philadelphia for broadcasting television, while the same frequency band is not used in New York City.
In general, “white space” refers to frequencies, usually allocated to a broadcasting service, that are not being used in a given location. Various proposals, including IEEE 802.11af, IEEE 802.22, and those from the White Spaces Coalition, advocate using white space to provide wireless data services. Such “white-space devices” are designed to detect the presence of unused bands and use these otherwise unused bands for data connectivity.